1. Field of the Invention
The present invention relates to the field of angioplasty. In particular, the present invention relates to an apparatus and method for facilitating the exchange of a dilatation balloon catheter on a guide wire.
2. Description of the Prior Art
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular diseases. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery.
Two types of dilatation catheters are xe2x80x9cover-the-wirexe2x80x9d catheters and xe2x80x9cnon-over-the-wirexe2x80x9d catheters. An over-the-wire catheter is one in which a separate guide wire lumen (sometimes called a xe2x80x9cthru lumenxe2x80x9d) is provided so that a guide wire can be used to establish a path through the stenosis. The dilatation catheter is then advanced over the guide wire until the balloon is positioned across the stenosis. One problem with the over-the-wire catheter is the inability to maintain the position of the guide wire within the vascular system when removing the catheter, and when exchanging it for one of a smaller (or larger) balloon diameter.
It is desirable to maintain the position of the guide wire across the stenosis during the exchange of catheters to ensure the safety and speed of the angioplasty procedure. Attempts to alleviate the problem of guide wire movement include the use of long or xe2x80x9cexchangeablexe2x80x9d guide wires, or extendable guide wires. These guide wires are of a length such that a proximal portion of the guide wire extends outside the patient""s body while a distal portion of the guide wire passes through the body and across the stenosis. Thus, during an exchange of balloon catheters on the wire, the guide wire position across the stenosis is maintained by holding onto a proximal segment of the guide wire from outside of the body. However, guide wire movement relative to the stenosis still occurs despite such external fixation of the guide wire. These guide wires also have the disadvantage of being cumbersome and difficult to handle while maintaining the guide wire position across the stenosis. For example, a length of guide wire of approximately 150 cm must be maintained outside the body (either by an extension or by a 300 cm long base guide wire). Furthermore, x-ray fluoroscopy must be used during the exchange in order for the operator to see the wire being held in position across the stenosis. This use of fluoroscopy results in an undesirable, excessive exposure of x-ray radiation to the patient and also to the attendant medical personnel.
A non-over-the-wire catheter (also called a xe2x80x9cfixed wirexe2x80x9d catheter) acts as its own guide wire, so that the exchange of catheters necessarily requires removal of the catheter/guide wire assembly from the stenosis area. Thus, when accomplishing an exchange with the xe2x80x9cnon-over-the-wirexe2x80x9d catheter, the path to the stenosis must be re-established when replacing the catheter with one having a different balloon diameter.
In both types of catheter/guide wire systems, it is difficult to effectively maintain or realign the guide wire across the stenosis. In addition, the exchange often requires more than one person to perform the procedure and requires extensive use of fluoroscopy resulting in excessive x-ray exposure to the patient.
Unlike previous catheter exchange systems which allow guide wire movement during an exchange at the distal end of the guide catheter and near the stenosis, the present invention has the advantage of fixing the guide wire position directly at the distal end of guide catheter and near the stenosis, thereby preventing guide wire movement relative to the stenosis.
The present invention is an improved apparatus for use in exchanging an over-the-wire balloon catheter on a guide wire, with the guide wire running through a guide catheter. The improved apparatus is a means for selectively engaging the guide wire within the guide catheter to restrict longitudinal movement of the guide wire relative to the guide catheter. The means for selectively engaging further include a means for urging a portion of the guide wire against an inner portion of the guide catheter.
In some preferred embodiments of the present invention, an inflation lumen extends longitudinally within the guide catheter. The inflation lumen has a proximal end and a distal end, with the distal end of the inflation lumen being within and adjacent to a distal end of the guide catheter. An inflatable balloon is in fluid communication with the distal end of the inflation lumen, and the inflatable balloon is of a size such that inflation of the balloon within the guide catheter restricts longitudinal movement of the guide wire relative to the guide catheter.
In one preferred embodiment, the inflation lumen is integral with a wall of the guide catheter and in fluid communication with an inflatable balloon that is fixed to a wall of the guide catheter. The inflation lumen provides a fluid path between the proximal end of the guide catheter and the inflatable balloon, wherein the balloon is inflated when pressure is applied to the fluid through the lumen. Upon inflation of the balloon, the guide wire is trapped between the balloon and the inner portion of the guide catheter, and longitudinal guide wire movement with respect to the guide catheter is limited.
In another preferred embodiment, the inflation lumen and an inflatable balloon both are separate from the guide catheter, and are thus movable longitudinally within the guide catheter. The inflation lumen provides a fluid path between the proximal end of the guide catheter and the inflatable balloon, wherein the balloon is inflated when pressure is applied to the fluid through the lumen. Upon inflation of the balloon, the guide wire is captured between the balloon and the guide. catheter, and longitudinal guide wire movement with respect to the guide catheter is limited.
In another preferred embodiment of the present invention, a captivation wire extends longitudinally within the guide catheter. The captivation wire has a distal end, a loop portion, and a proximal end. The distal end of the captivation wire is secured to the guide catheter, and the loop portion of the captivation wire is within and just proximal to the distal end of the guide catheter. The loop portion has an open loop state, whereby unrestricted longitudinal movement of the guide wire through the loop portion and relative to the guide catheter is permitted. The loop portion also has a closed loop state, whereby longitudinal movement of the guide wire relative to the guide catheter is limited.
In one embodiment, the captivation wire extends longitudinally through and is slidably received in a lumen formed in a wall of the guide catheter. A spiraled recess is formed within an inner wall of the guide catheter to receive the loop portion of the captivation wire when in its open loop state. A tab member is connected to the proximal end of the captivation wire and is mounted to the proximal end of the guide catheter. The tab member is movable longitudinally with respect to the guide catheter between a first distal position and a second proximal position. When the tab member is in its first distal position, the captivation wire is in the open loop state and when the tab member is in its second proximal position, the captivation wire is in the closed loop state. The tab member also includes detent means to selectively retain the tab member in the first distal position or the second proximal position.
The unique and inventive method for limiting a guide wire in a guide catheter from longitudinal movement with respect to the guide catheter involves two simple steps: (1) providing a means for selectively engaging the guide wire within the guide catheter, and (2) manipulating the means for engaging to force the guide wire against an inner portion of the guide catheter, thereby fixing the guide wire position with respect to the guide catheter. Preferably, the means for engaging the guide wire is positioned within the guide catheter adjacent a distal end of the guide catheter. The guide wire position is thus fixed at a location somewhat close to the stenosis, as opposed to trying to hold the guide wire in position by grasping the guide wire adjacent its proximal end, at a location outside of the body and very remote from the stenosis.
In one embodiment of the inventive method, the means for engaging the guide wire is an inflatable wire-captivation balloon. The wire-captivation balloon is provided within the guide catheter and inflated to a size such that the balloon forces the guide wire against an inner portion of the guide catheter, thereby fixing the guide wire position with respect to the guide catheter.
To exchange a first over-the-wire catheter on a guide wire in a patient""s vascular system for a second over-the-wire catheter on the guide wire, this inventive exchange method includes a first step of providing the inflatable wire-captivation balloon within the guide catheter. Next, a proximal end of the guide wire is held outside the vascular system to maintain position of the guide wire longitudinally relative to the guide catheter, while the balloon of the first over-the-wire catheter is moved on the guide wire into the guide catheter to a position that is proximal of the wire-captivation balloon. The wire-captivation balloon is then inflated to maintain the position of the guide wire relative to longitudinal movement with respect to the guide catheter. Once the guide wire position is fixed within the guide catheter, the proximal end of the guide wire is released. Then, the first over-the-wire catheter is withdrawn from a proximal end of the guide wire, and a second over-the-wire catheter is installed onto the proximal end of the guide wire. The balloon of the second over-the-wire-catheter is moved to a position just proximal of the wire-captivation balloon, and then the proximal end of the guide wire is again held outside of the vascular system to maintain position of the guide wire longitudinally relative to the guide catheter and vascular system. Next, the wire-captivation balloon is deflated to release the guide wire from its fixed position relative to the guide catheter, and finally the second over-the-wire catheter is moved distally of the wire-captivation balloon and across the lesion for further dilatation.
In another embodiment of the inventive method, the means for engaging the guide wire is a wire-captivation wire. The wire-captivation wire is provided within the guide catheter and when a loop portion of the wire-captivation wire is closed, the guide wire is forced against an inner portion of the guide catheter, thereby fixing the guide wire position relative to the guide catheter.
An exchange of over-the-wire catheters by the inventive method using the wire-captivation wire requires a wire-captivation wire within the guide catheter that has a looped portion through which the guide wire extends. In use, the looped portion closes to trap the guide wire against an inner portion of the guide catheter and opens to release the guide wire. The wire-captivation wire replaces the wire-captivation balloon of the previous exchange method and in particular, the looped portion of the wire-captivation wire effectively replaces the inflatable wire-captivation balloon. All the steps of the previous exchange method are duplicated except for the following: (1) instead of inflating the balloon to a size such that movement of the guide wire longitudinally relative to the guide catheter is limited, the looped portion of the captivation wire is closed to a size such that movement of the guide wire longitudinally relative to the guide catheter is limited, and (2) instead of deflating the inflatable balloon to release the guide wire from its fixed position relative to the guide catheter, the looped portion is opened to release the guide wire.